To Join or Not to Join? Danish Nazi Collaborators and the German Occupation

EPSA 2025, Madrid

Frederik
Thieme

Humboldt-Universität zu Berlin

Salma
Mahamed

Copenhagen Business School

June 27, 2025

Motivation 🪖

Overview

  • Question: Why did membership in the DNSAP surge after the German occupation?
  • 💡 Argument:
    • Context: economic stability, democratic norms, small Jewish population, anti-German sentiment
    • opportunistic entry into the DNSAP by older, higher status individuals from civil service or agrarian sector
    • entries from across the country and close to German military centers
  • ️⚙️ Data & Method:
    • Bovrup-Archive: DNSAP member list (N = 22,000), added geographic and sociodemographic info
    • RDD with entry date as running variable, cutoff at 9 April 1940
  • 📊 Results:
    • older, higher status individuals join
    • more civil servants, no change on sector
    • driven by members from German border region

Membership surge post-invasion 📈

Theory

  • General Incentive Model: Political participation is driven by rational cost-benefit calculations (e.g. Whiteley et al. 2021; Poletti, Webb, and Bale 2019)
  • Beyond Ideology: Party membership under can reflect self-interest rather than ideological alignment
  • Our extension:
    • Under occupation, party entry reflects self-preservation, not ideology

Argument

  • pre-war Denmark 🇩🇰:
    • stable economy, democratic norms, small Jewish population, anti-German sentiment
  • opportunism hypothesis: strategic entry into the party under the uncertainty of the invasion to secure position, future benefits
    • Age: older, more established, “more to lose”
    • Social Status: higher education, skill and class; secure position
    • Sector: civil service, strong uncertainty; agrarian, close economic ties
    • Location: across the country, but closer to German military centers

Data 💾

  • DNSAP member list
    • name, address, date of birth, date of entry, job
  • data extension:
    • gender, inferred from first names
    • location, Google’s geolocation API
    • education and skill level, job sector with ChatGPT API
    • social class, HISCO classification matching

Empirical Strategy

  • base associations:
    • OLS with occupation dummy as IV, controlling for age and gender
    • note: see draft for results
  • regression discontinuity design (RDD):
    • running variable: date of entry
    • cutoff: 9 April 1940, German invasion
    • bandwidth selection automatic for now
    • modelling assumptions: linear, quadratic, cubic

Results (1/2)

Results (2/2)

Interpretation

Summary & Alternative Interpretation 🤔

  • Mixed evidence for opportunism:
    • Older, high-status, and civil servant membership increased post-occupation.
    • No surge among farmers; concentration near the German border.
  • Alternative explanation – Normalization:
    • Limited room for opportunism: Danish self-rule remained intact, DNSAP stayed fringe, and Germany withheld formal support
    • Occupation reduced social sanctions for Nazi affiliation
    • High-status, risk-averse individuals may have waited until ideological alignment became socially safer
    • Explains geographic and sectoral patterns without assuming opportunistic gain-seeking.

Contribution & Outlook 🔭

  • Sheds light on collaboration under occupation without direct military rule \(\rightarrow\) political behavior under constrained democracy
  • Leverages newly enriched historical data for disaggregated, causal analysis
  • Shifts focus from resistance to collaboration in occupied states

Next steps:

  • Trace post-war political consequences of collaboration using local election data
  • Analyze spatial interplay between collaboration and resistance using resistance member data

Thank you for your attention.

Questions or feedback? Hit me up:

Literature 📚

Poletti, Monica, Paul Webb, and Tim Bale. 2019. “Why Do Only Some People Who Support Parties Actually Join Them? Evidence from Britain.” West European Politics 42 (1): 156–72. https://doi.org/10.1080/01402382.2018.1479921.
Whiteley, Paul, Erik Larsen, Matthew Goodwin, and Harold Clarke. 2021. “Party Activism in the Populist Radical Right: The Case of the UK Independence Party.” Party Politics 27 (4): 644–55. https://doi.org/10.1177/1354068819880142.